Two million cases of Salmonella food poisoning are estimated to occur each year in the United States alone. Acute symptoms of this disorder include nausea, vomiting, diarrhea, cold chills, fever, and exhaustion. A small percentage of those afflicted (0.1%, or 2,000 people annually in the United States) die from Salmonella poisoning, with these victims usually being infants, the sick, and the elderly. See Generally T. Roberts, The Economic Losses Due to Selected Foodborne Diseases. 5-6 (1986) (Economic Research Service/USDA, 1301 New York Avenue, N.W., Room 1108, Washington, DC 20005-4788).
Of all potential sources of Salmonella poisoning, poultry products have been identified as the primary source. Thus, breaking the chain of salmonellae being passed from one generation of birds to the next has been the goal of poultry researchers for at least twenty-five years. However, a special type of symbiotic relationship (a commensal relationship) exists between a host bird and salmonellae living within it. Because the bird's health is not impaired by the salmonellae, it does little to exclude the organism or to try to rid itself of the organism once it has been colonized. The prevention of salmonellae colonization in poultry is therefore extremely difficult.
One approach to preventing salmonellae colonization of poultry is competitive exclusion. See generally H. Pivnick and E. Nurmi, Developments in Food Microbiologly 1, 41 (1982). In this approach, a probiotic bacterial culture (that is, a bacterial culture which has a beneficial effect on the animal to which it is administered) is introduced into a bird's digestive tract prior to its colonization by Salmonella. The probiotic bacterial culture is selected to occupy the same environmental niche in the bird's digestive tract that the Salmonella would occupy, so that Salmonella which subsequently pass into the bird's digestive tract tend to be excluded by the bacteria which have been purposely introduced. Competitive exclusion is a promising method of preventing Salmonella from colonizing birds which are raised in a comparatively Salmonella-free environment. Unfortunately, there are numerous potential sources of salmonellae contamination in a modern poultry operation, including chicks, feed, rodents, birds, insects, and the transportation and processing procedures to which the birds are subjected. These diverse sources of contamination make it difficult to administer a competitive exclusion culture to a bird before it is first colonized by Salmonella.
An object of the present invention is, accordingly, to provide a new technique for introducing probiotic bacteria into the digestive tracts of birds. A more particular object of the present invention is to provide a new technique for competitively excluding Salmonella from the digestive tract of birds prior to colonization by Salmonella.